1. Field of the Invention
The present invention relates to a temperature estimating apparatus, a method for controlling the same, and an image display apparatus.
2. Description of the Related Art
In recent years, the local dimming (partial dimming or extinction) control is available as a control method for controlling a backlight which radiates the light onto a back surface of a liquid crystal panel of a liquid crystal display apparatus (LCD: Liquid Crystal Display). In the local dimming control, the backlight is divided into a plurality of light source blocks, and the luminance is controlled for each of the light source blocks depending on an input image. Accordingly, the contrast is enhanced, and the electric power consumption is suppressed.
LED (Light Emitting Diode), in which the electric power consumption is decreased and the high control response speed is obtained, is used in some cases as a light source of the backlight in order to realize the local dimming control. Further, in order that the luminance can be controlled partially or locally, the backlight is constructed in some cases by a plurality of LEDs, and the LEDs are divided into a plurality of light source blocks for which the luminance can be controlled independently.
In general, in the case of LED, the luminance and the wavelength of the light emission are changed depending on the temperature. The amount of change differs depending on the light emission color (red, green, blue). Further, the time-dependent change differs depending on each of the light emission colors.
For example, in the case of Japanese Patent Application Laid-open Nos. 2009-42651 and 2009-42652, the change of the light emission is detected by using a temperature sensor for LED and/or a color sensor for detecting the color balance so that the correction control is performed in order to provide the stable display. In the case of a display apparatus described in Japanese Patent Application Laid-open No. 2007-165632, such a method is also suggested that the ambient temperature of LED and the voltage between terminals are detected respectively to estimate the temperature of LED. In the case of a display apparatus described in Japanese Patent Application Laid-open No. 2007-240666, such a method is also suggested that the internal temperature of the display apparatus and the temperature of a part or parts are estimated without using any temperature sensor.